1. Field of the Invention
This invention relates to a hydraulic door operating system which may be either manually or automatically operated and in particular to such a system which is specially adapted for the liftgate of a minivan or sport utility vehicle.
2. Discussion of the Prior Art
The liftgate of a minivan or sport utility vehicle that is hinged about a horizontal axis at the top of the gate usually has gas charged cylinders at each side of the gate which provide an opening force and help hold the gate open after it is in its fully open position. These gates are usually manually operated by unlatching the gate and lifting it and manually closing it. Usually, at some angle of the gate between fully open and fully closed, the force provided by the gas charged cylinders equals the force of gravity tending to close the gate.
As an enhancement, it is desirable to provide such gates with an automatic system for opening and closing them. Ideally, such a system should be transparent to the user when manually opening and closing the gate. In other words, to manually open and close the liftgate of a system to which the invention has been applied, the user should not have to deviate from the usual opening and closing procedure employed with non-automatic, conventional liftgates. The user should just be able to walk up to the gate (after it is unlatched), lift the gate as usual, and close the gate as usual, overriding the automatic operation of the gate.